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MJS Pile Construction Technology: Principles, Process, and Quality Control

Introduction

The MJS (Metro Jet System) pile method, also known as the Omni-Directional High-Pressure Jet Grouting technique, has been widely adopted in foundation treatment, seepage control for excavation support walls, basement waterproofing, and emergency rescue projects. Recognized for its effectiveness, this method has been successfully applied in numerous projects supervised by our company. This article explores the construction technology and quality control measures of MJS piles, providing valuable insights for industry professionals.

1. Principles and Characteristics of MJS Pile Construction

1.1 Principles of MJS Pile Technology

Originally developed to address slurry discharge and environmental concerns in horizontal jet grouting, the MJS method is now extensively used in foundation reinforcement, seepage prevention, and underground structure waterproofing. Key features include:

  • Multi-hole pipe and forced slurry suction system – Ensures controlled underground pressure and slurry discharge, minimizing ground deformation.

  • Pressure monitoring and adjustment – Stabilizes underground pressure, ensuring consistent pile diameter and reduced environmental impact.

1.2 Key Features of MJS Technology

1.2.1 Omni-Directional Construction

  • Capable of horizontal, vertical, and inclined jet grouting at any angle.

  • Maximum effective reinforcement depth: up to 100m.

1.2.2 Large Diameter and High-Quality Piles

  • Initial jet pressure: 40 MPa

  • Flow rate: 90–130 L/min

  • Average lifting speed: 2.5–3.3 cm/min

  • Pile diameter: 2–2.8 m (depending on soil conditions)

  • Stable coaxial air pressure (0.7 MPa) enhances pile integrity.

1.2.3 Minimal Environmental Impact

  • Forced slurry discharge prevents excessive underground pressure, reducing ground deformation.

  • Deep excavation stability is ensured through real-time pressure control.

1.2.4 Reduced Slurry Pollution

  • Dedicated discharge pipes facilitate centralized slurry management.

  • Prevents slurry leakage into soil, water, or underground pipelines.

2. MJS Pile Construction Process

2.1 Construction Preparation

  • Pile positioning: Use a total station for accurate alignment (<50mm deviation).

  • Underground utility detection: Excavate trenches (1m depth) to locate pipelines before drilling.

  • Slurry and waste management:

    • 100–130% slurry return requires proper sedimentation and disposal.

    • Implement mud-water separation systems where necessary.

2.2 Drilling and Alignment

  • Drill rig setup: Ensure vertical alignment (<0.5% deviation).

  • Pilot hole drilling:

    • Depth: 1m deeper than design.

    • Use bentonite slurry for hole stability.

    • Install 219mm casing in weak soil layers to prevent collapse.

2.3 MJS Jet Grouting Execution

  1. Nozzle positioning: Lower to design depth and rotate for 60+ seconds to stabilize pressure.

  2. Jet grouting parameters:

    • Pressure: 40 MPa

    • Lifting speed: Adjusted based on soil conditions.

  3. Slurry discharge: Forced suction maintains pressure balance.

2.4 Post-Construction Procedures

  • Pile top treatment: Stop grouting 100mm above design elevation.

  • Equipment cleaning: Flush drill rods and pumps before relocation.

3. Quality Control Measures

3.1 Pre-Construction Checks

  • Material testing: Verify cement quality and water suitability.

  • Equipment calibration: Ensure pressure gauges, flow meters, and pumps function correctly.

  • Test grouting: Conduct ≥2 trial piles to adjust parameters.

3.2 In-Process Monitoring

  • Real-time adjustments: Monitor drilling angle, speed, and grouting pressure.

  • Data recording: Document pressure/flow rates per 1m lift or at soil layer transitions.

3.3 Post-Construction Verification

  • Core sampling (after 28 days): Test for compressive strength and uniformity.

  • Inspection frequency: 1–2% of total piles (minimum 1 test for <20 piles).

4. Safety and Environmental Measures

  • Electrical safety: Ground all equipment; certified electricians only.

  • Mechanical hazards: Lockout/tagout during maintenance.

  • High-pressure systems: Regular inspection of hydraulic/pneumatic lines.

  • Waste management: Use sedimentation ponds and dust suppression (e.g., mist cannons).

5. Common Quality Issues & Solutions

(Detailed case-specific troubleshooting can be provided upon request.)

Conclusion

The MJS pile method outperforms conventional jet grouting techniques in diameter, depth, and environmental safety. Its compatibility with H-beam reinforcement and additive-enhanced slurries makes it ideal for waterproof curtains and soft soil stabilization. As underground construction grows, MJS technology will play an increasingly vital role in ensuring high-quality, low-impact foundation solutions.

 

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